We are currently in the midst of a mass extinction event, the sixth major extinction in Earth’s history. Species are going extinct at an alarming rate, up to 10,000 times higher than the natural background rate. Humans are the main cause of the current crisis through activities like habitat destruction, overhunting, pollution, and climate change. Some scientists estimate that up to half of all species on Earth could be at risk of extinction by 2100 if trends continue. Understanding the causes, assessing the risks, and enacting solutions are crucial steps to stemming biodiversity loss.
What is an extinction event?
An extinction event or mass extinction occurs when a significant percentage of the Earth’s species go extinct in a relatively short geological timescale. The fossil record shows that there have been five major extinction events in the past, including:
- Ordovician-Silurian extinction 433 million years ago – 86% of species lost
- Late Devonian extinction 364 million years ago – 75% species lost
- Permian-Triassic extinction 252 million years ago – 96% species lost
- Triassic-Jurassic extinction 201 million years ago – 80% species lost
- Cretaceous-Paleogene extinction 66 million years ago – 76% species lost
The Cretaceous-Paleogene extinction is best known for wiping out the dinosaurs (except birds). These past events were caused by catastrophic changes like massive volcanic eruptions, asteroid impacts, and climate shifts. Extinction events reshape the course of evolution as new groups of organisms take over ecological niches vacated by extinct species.
Key indicators of the 6th extinction
Scientists measure biodiversity loss in the current extinction in several key ways:
Species extinction rates
– Background extinction rate is estimated to be around 1-5 species per year.
– Current extinction rates are estimated to be 100 to 1,000 times higher than background levels.
– Up to 30% of amphibians, 21% of mammals, and 12% of birds are threatened with extinction currently.
Population declines
– Global wildlife populations have declined by 68% on average since 1970.
– Bird and mammal populations in particular have declined rapidly in the last 50 years.
– 81% decline in freshwater wildlife populations since 1970.
Changes in species distribution and abundance
– Geographic ranges and local abundance of many species are declining.
– Indicators like the Living Planet Index show a 68% overall decline in monitored vertebrate species since 1970.
Loss of biodiversity hotspots
– High biodiversity regions like tropical rainforests and coral reefs are losing species rapidly due to deforestation, bleaching events, etc.
– Over 80% of original primary forest cover has been cleared in regions like the Atlantic Forest of Brazil.
Increased extirpations and extinctions
– Many populations of species are going extinct locally, leading to global extinction risk.
– Extinctions have already occurred in well-studied groups like mammals, birds, and amphibians.
How do scientists measure extinction risk?
The International Union for Conservation of Nature (IUCN) Red List of Threatened Species is the global standard for evaluating extinction risk for plants and animals. Species are classified into categories:
| IUCN Red List Category | Definition |
|---|---|
| Extinct (EX) | No living individuals left |
| Extinct in the Wild (EW) | Survives only in captivity |
| Critically Endangered (CR) | Extremely high risk of extinction |
| Endangered (EN) | Very high risk of extinction |
| Vulnerable (VU) | High risk of extinction |
| Near Threatened (NT) | May be at risk soon |
| Least Concern (LC) | Lowest risk |
Threatened species (CR, EN, VU) and extinct species make up the highest categories of risk. Nearly 28% of assessed species worldwide are currently threatened.
What is causing the 6th mass extinction?
Unlike past extinction events caused by natural events, human activities are almost entirely responsible for the accelerating biodiversity crisis:
Habitat destruction and fragmentation
– Agriculture, logging, infrastructure development, and urbanization destroy and fragment natural habitats.
– Over 50% of liveable land area is used for agriculture currently.
– Tropical rainforest area has declined by over 80 million hectares since 1990.
Overexploitation of species
– Overhunting, overfishing, illegal wildlife trade, and harvesting for traditional medicine threaten many species.
– Humans have increased the extinction rate of vertebrates 100-1000 fold higher by overexploitation.
Invasive alien species
– Non-native species introduced by human travel and trade can become invasive and threaten native species.
– Invasive predators, herbivores, and pathogens have contributed to many extinctions globally.
Pollution
– Pesticides, plastics, oil spills, chemical waste, and other pollutants poison wildlife and habitats.
– Ocean plastic pollution in particular affects over 800 marine species.
Climate change
– Rising global temperatures disrupt ecosystems, seasons, and species interactions.
– 15-37% of species may be committed to extinction by 2050 due to climate change.
Why does extinction matter?
High extinction rates in the modern era are an existential threat to global biodiversity and human societies:
Ecological effects
– Extinction cascades through ecosystems causing further species loss.
– Declines in key species like pollinators and seed dispersers affect crucial processes.
– Biodiversity increases ecosystem resilience to stresses like climate change.
Loss of potential knowledge and resources
– Undiscovered medical or agricultural benefits disappear when species go extinct.
– Crucial ecological knowledge about how natural systems work is lost.
Ethical considerations
– Many consider biological diversity to have inherent value beyond human use.
– Conservation is an ethical responsibility for caretakers of the environment.
Economic impacts
– Industries like agriculture, forestry, and fishing depend on healthy ecosystems.
– Ecosystem services like crop pollination have immense economic value that is diminished.
Is it too late to act?
While the biodiversity crisis is dire, there is still time to prevent further deterioration and extinctions through systemic changes and conservation action:
Habitat conservation
– Increase protected nature reserve areas to cover 30% or more of land and ocean.
– Restore and reconnect fragmented habitats and ecosystems.
Sustainable use of species
– Implement hunting, fishing, and logging regulations based on science.
– Crack down on illegal poaching and wildlife trade.
Control of invasives
– Rapidly detect and eradicate new invasive species.
– Manage existing invasive populations through biocontrol, removal, etc.
Mitigation of climate change
– Transition rapidly away from fossil fuels to renewable energy.
– Protect species by assisting migration and adaptation.
Public education
– Teach the value of biodiversity and extinction crisis in schools.
– Encourage lifestyle changes that reduce environmental impact through media.
Funding and policy changes
– Increase conservation funding from governments and private organizations.
– Pass laws and agreements supporting biodiversity strategies nationally and internationally.
Conclusion
Earth is currently in the throes of a sixth mass extinction event caused by human activities like habitat loss and overexploitation. Rapid decline in species populations, geographic ranges, and overall biodiversity threatens vital ecosystem services and human societies. While the extinction crisis is dire, implementing solutions like expanding protected areas, controlling invasive species, mitigating climate change, and enacting supportive policies can help stem biodiversity loss. Public education to encourage conservation values and action is also essential. With immediate, decisive action, we can still preserve much of the remaining biodiversity on Earth for future generations.